I have a strange question. I was extracting RNA using Qiamp minikit and at the last step I found out that there was no elution buffer left. So as I had a number of samples, I decided to freeze the columns to which RNA was bound.Would that be possible to thaw the columns the next day and elute RNA?

Well, RNA is pretty unstable and I am quite certain the recovery is far from optimal after a freeze-thaw cycle, but I guess nothing prevents you from trying (remember to tell us what was the outcome!)

If it was DNA, I think you might be able to do that without much problems.

One option, though somewhat bizarre, would be to fill your columns with some RNA preservation solution that helps to keep RNA strands intact during freezing and thawing before freezing the columns - in case you had some in your lab when running out of elution buffer. I think Qiagen is one of the companies that produces those!